JX Crystals has been developing thermophotovoltaic (TPV) generators for small-scale applications. These applications include heating stoves for off-grid cabins, outdoor battery chargers for the Army, and residential furnaces for combined heat and power.
JX Crystals TPV technology is based on three core elements: low bandgap TPV cells, high packing density shingle circuits, and antireflection (AR) coated refractory metal matched infrared (IR) emitters (patent references).
In the applications that we have described to date, hydrocarbon fuel is burned inside the emitter and the cell arrays are mounted outside the IR emitter. However, there are high temperature industrial processes where large burners heat large spaces.
In these applications, TPV could be used to produce electricity for various needs, since burners are already present, heat is being used, and heat recovery means already are designed into the process.
FIG. 1 shows an example of one such high temperature large-scale industrial process, i.e. a glass-melting furnace. A need exists to design a TPV generator for use in these high temperature industrial processes. This TPV system will need to be easily inserted into the high temperature zone without disrupting the process. It will also need to be easily accessed for maintenance. Furthermore, it will have to produce economical electric power. One benefit of such a TPV system would be that it could produce back up power in the event of a power failure so that the process could run in an idle state. Without backup power, considerable damage will be done to the furnace and its contents if the furnace cools down.
The inventive emitter for use with a generator is a tube closed at one end heated from its outside with a water-cooled photovoltaic converter array mounted inside.
In the preferred embodiment for glass-melting application, several of these TPV tubes may be inserted through holes in the insulation into the port sections between the glass-melting furnace and the regenerators. Any one of these tubes may be removed for maintenance at any time and replaced with a closure, such as but not limited to a brick, to close off the hole, without affecting the industrial process.
In a preferred embodiment, the outer emitter tube may be a SiC or KANTHAL (iron-chromium-aluminum alloy) tube. This tube may be lined on its inside preferably with AR coated tungsten foil. Alternatively, the tungsten could be deposited on the inner tube surface as a film followed by the AR coating.
The photovoltaic converter array may consist of a polygonal array of shingle circuits where the circuits are fabricated using low bandgap GaSb cells. The water-cooled photovoltaic converter array may be mounted on a base plate and this base plate may be clamped to a flange on the SIC or KANTHAL tube. A metal o-ring seals the base plate to the tube flange so that the inner space between the photovoltaic array and the AR coated tungsten emitter can be back filled with an inert gas such as argon. Electrical and water cooling feeds are provided through the base plate.
This industrial TPV generator is actually simpler than small-scale TPV generators because no burners or recuperators are required in the TPV generator design. These are already provided in the industrial process. This leads to lower cost.
These and further and other objects and features of the invention are apparent in the disclosure, which includes the above and ongoing written specification, with the drawings.